Engineering a detect and destroy skin probiotic to combat methicillin-resistant Staphylococcus aureus.

The prevalence and virulence of pathogens such as methicillin-resistant Staphylococcus (S.) aureus (MRSA), which can cause recurrent skin infections, are of significant clinical concern. Prolonged antibiotic exposure to treat or decolonize S. aureus contributes to development of antibiotic resistance, as well as depletion of the microbiome, and its numerous beneficial functions. We hypothesized an engineered skin probiotic with the ability to selectively deliver antimicrobials only in the presence of the target organism could provide local bioremediation of pathogen colonization. We constructed a biosensing S. epidermidis capable of detecting the presence of S. aureus quorum sensing autoinducer peptide and producing lysostaphin in response. Here, we demonstrate in vitro activity of this biosensor and present and discuss challenges to deployment of this and other engineered topical skin probiotics

Controlling the Growth of the Skin Commensal Staphylococcus epidermidis Using d-Alanine Auxotrophy.

Using live microbes as therapeutic candidates is a strategy that has gained traction across multiple therapeutic areas. In the skin, commensal microorganisms play a crucial role in maintaining skin barrier function, homeostasis, and cutaneous immunity. Alterations of the homeostatic skin microbiome are associated with a number of skin diseases. Here, we present the design of an engineered commensal organism, Staphylococcus epidermidis, for use as a live biotherapeutic product (LBP) candidate for skin diseases. The development of novel bacterial strains whose growth can be controlled without the use of antibiotics or genetic elements conferring antibiotic resistance enables modulation of therapeutic exposure and improves safety. We therefore constructed an auxotrophic strain of S. epidermidis that requires exogenously supplied d-alanine. The S. epidermidis NRRL B-4268 Δalr1 Δalr2 Δdat strain (SEΔΔΔ) contains deletions of three biosynthetic genes: two alanine racemase genes, alr1 and alr2 (SE1674 and SE1079), and the d-alanine aminotransferase gene, dat (SE1423). These three deletions restricted growth in d-alanine-deficient medium, pooled human blood, and skin. In the presence of d-alanine, SEΔΔΔ colonized and increased expression of human β-defensin 2 in cultured human skin models in vitro. SEΔΔΔ showed a low propensity to revert to d-alanine prototrophy and did not form biofilms on plastic in vitro. These studies support the potential safety and utility of SEΔΔΔ as a live biotherapeutic strain whose growth can be controlled by d-alanine.IMPORTANCE The skin microbiome is rich in opportunities for novel therapeutics for skin diseases, and synthetic biology offers the advantage of providing novel functionality or therapeutic benefit to live biotherapeutic products. The development of novel bacterial strains whose growth can be controlled without the use of antibiotics or genetic elements conferring antibiotic resistance enables modulation of therapeutic exposure and improves safety. This study presents the design and in vitro evidence of a skin commensal whose growth can be controlled through d-alanine. The basis of this strain will support future clinical studies of this strain in humans

The diagnostic role of gut feelings in general practice A focus group study of the concept and its determinants

Contains fulltext : 81297.pdf (publisher's version ) (Open Access)BACKGROUND: General practitioners sometimes base clinical decisions on gut feelings alone, even though there is little evidence of their diagnostic and prognostic value in daily practice. Research into these aspects and the use of the concept in medical education require a practical and valid description of gut feelings. The goal of our study was therefore to describe the concept of gut feelings in general practice and to identify their main determinants METHODS: Qualitative research including 4 focus group discussions. A heterogeneous sample of 28 GPs. Text analysis of the focus group discussions, using a grounded theory approach. RESULTS: Gut feelings are familiar to most GPs in the Netherlands and play a substantial role in their everyday routine. The participants distinguished two types of gut feelings, a sense of reassurance and a sense of alarm. In the former case, a GP is sure about prognosis and therapy, although they may not always have a clear diagnosis in mind. A sense of alarm means that a GP has the feeling that something is wrong even though objective arguments are lacking. GPs in the focus groups experienced gut feelings as a compass in situations of uncertainty and the majority of GPs trusted this guide. We identified the main determinants of gut feelings: fitting, alerting and interfering factors, sensation, contextual knowledge, medical education, experience and personality. CONCLUSION: The role of gut feelings in general practice has become much clearer, but we need more research into the contributions of individual determinants and into the test properties of gut feelings to make the concept suitable for medical education

Inhibition of Antibiotic Efflux in Bacteria by the Novel Multidrug Resistance Inhibitors Biricodar (VX-710) and Timcodar (VX-853)

Inhibitors of mammalian multidrug efflux, such as the plant alkaloid reserpine, are also active in potentiating antibiotic activity by inhibiting bacterial efflux. Based on this precedent, two novel mammalian multiple drug resistance inhibitors, biricodar (VX-710) and timcodar (VX-853), were evaluated for activity in a variety of bacteria. Both VX-710 and VX-853 potentiated the activity of ethidium bromide (EtBr), a model efflux substrate, against three clinically significant gram-positive pathogens: Staphylococcus aureus, Enterococcus faecalis, and Streptococcus pneumoniae. Similar to reserpine, VX-710 and VX-853 directly blocked EtBr efflux in S. aureus. Furthermore, these compounds were effective in lowering the MICs of several clinically used antibiotics, including fluoroquinolones, suggesting that VX-710 and VX-853 are representatives of a new class of bacterial efflux inhibitors with the potential for use in combination therapy

Structures of human dihydroorotate dehydrogenase in complex with antiproliferative agents

AbstractBackground: Dihydroorotate dehydrogenase (DHODH) catalyzes the fourth committed step in the de novo biosynthesis of pyrimidines. As rapidly proliferating human T cells have an exceptional requirement for de novo pyrimidine biosynthesis, small molecule DHODH inhibitors constitute an attractive therapeutic approach to autoimmune diseases, immunosuppression, and cancer. Neither the structure of human DHODH nor any member of its family was known.Results: The high-resolution crystal structures of human DHODH in complex with two different inhibitors have been solved. The initial set of phases was obtained using multiwavelength anomalous diffraction phasing with selenomethionine-containing DHODH. The structures have been refined to crystallographic R factors of 16.8% and 16.2% at resolutions of 1.6 Å and 1.8 Å for inhibitors related to brequinar and leflunomide, respectively.Conclusions: Human DHODH has two domains: an α/β-barrel domain containing the active site and an α-helical domain that forms the opening of a tunnel leading to the active site. Both inhibitors share a common binding site in this tunnel, and differences in the binding region govern drug sensitivity or resistance. The active site of human DHODH is generally similar to that of the previously reported bacterial active site. The greatest differences are that the catalytic base removing the proton from dihydroorotate is a serine rather than a cysteine, and that packing of the flavin mononucleotide in its binding site is tighter